Pump driving mechanism

ABSTRACT

A pump driving mechanism of this applications is formed by supporting a piston body 3 provided with a piston rod 9 and an elastic arm 18 movable in directions vertical to reciprocally moving directions of the piston body, between respective free ends of a pair of elastic leg pieces 16 and 17 fixed at one end and freed at the other end, and connecting an eccentric shaft 23 driven to be rotated by a motor 22 to a shaft bearing 21 formed at a free end of the elastic arm 18, whereby a low noise reciprocating movement within a cylinder 14 is provided to a piston rod 9 by rotations of the eccentric shaft 23.

TECHNICAL FIELD

This invention relates to pump driving mechanisms and, moreparticularly, to a pump driving mechanism wherein a piston body providedwith a shaft bearing part for a driving source is supported throughelastic legs and the driving source is connected to the shaft bearingpart to convert motions of the driving source to reciprocating motions.

BACKGROUND ART

Generally, in the pump driving mechanism, a pure reciprocating motionmust be given to a piston to prevent water leakage and a contrivance toachieve that motion, such as a crank connection is required.

Therefore, in such conventional pump driving mechanisms as the one whichhas been adopted in a water feeding device 70 of, for example, FIG. 15,a driving force of an output shaft 72 of an electric motor 71 for a pumpis transmitted to a driving gear 74 through a gear 73. An eccentricrotary motion of an eccentric pin 75 provided to project on the drivinggear 74 is converted to a reciprocating motion through a slider 76 andpiston joint 77, and a piston 78 is correctly driven to reciprocatewithin a cylinder 79. In such mechanism, however, a large noise has beengenerated when it is driven and the energy loss has been large for thefollowing reasons. That is, there are seven places in which therespective elements slide in contact with each other, namely, betweenthe eccentric pin 75 and the slider 76, between the slider 76 and thepiston joint 77, between the piston joint 77 and the driving gear 74,between the slider 76 and the driving gear 74, between a piston rod 80and a shaft bearing 81, between the gear 73 and the driving gear 74 andbetween the driving gear 74 and a reduction gear shaft 82 and the noisehas been large.

DISCLOSURE OF THE INVENTION

Therefore, a first object of the present invention is to provide a pumpdriving mechanism wherein the sliding contacts are few and the noiseupon the driving is low.

A second object of the present invention is to provide a pump drivingmechanism wherein the size of the mechanism is minimized and the drivingload is reduced.

A third object of the present invention is to provide a pump drivingmechanism wherein vertical motions and rolling motions of the pistonbody in the reciprocating motion are prevented and any deterioration inperformances due to a generation of clearance between the pison and thecylinder is prevented.

A fourth object of the present invention is to provide a pump drivingmechanism of a thin type.

Other objects of the present invention will be gradually made clear bythe following explanations with reference to embodiments.

Accordingly, in the present invention, a piston body is supportedbetween respective free ends of a pair of elastic leg pieces fixed atone end and made free at the other end, a piston rod and shaft bearingpart are formed in said piston body, an eccentric shaft driven to berotated by a motor is connected to the shaft bearing part and the pistonbody is reciprocated, to thereby solve the foregoing conventionalproblems.

Further, in the present invention, the pair of elastic leg pieces areformed of U-shaped bent pieces and a substantial length of the elasticleg piece is secured within a limited space to attain the foregoingsecond object; the pair of U-shaped elastic leg pieces are folded backat half the entire length so as to cancel the rolling of the piston bodyby the both folded back pieces and to thereby provide a purereciprocating motion to the piston body and attain the second and thirdobjects; the pair of elastic leg pieces are connected with each otherthrough connecting pieces and any nonuniform deflections of therespective elastic legs are eliminated to thereby attain the thirdobject; an elastic arm movable in directions vertical to reciprocatingdirections of the piston body is provided with a shaft bearing and aneccentric shaft is inserted into the shaft bearing so that motions ofthe eccentric shaft in the direction intersecting at right angles thereciprocating motions of the piston will be absorbed by rocking motionsof the elastic arm while the eccentric shaft and shaft bearing areround-hole-connected with each other to reduce noise generating sourcesto thereby attain the first object; and timing pulleys are connectedthrough a timing belt to arrange the driving mechanism and drivingsource (motor) in parallel with each other to thereby attain the fourthobject.

Explanations shall be made in the followings with reference to drawingsshowing embodiments of the present invention.

BRIEF EXPLANATION OF THE DRAWINGS

The drawings show embodiments of a pump driving mechanism of the presentinvention, in which:

FIG. 1 is a perspective view of an appearance of the drive;

FIG. 2 is a sectioned view on line P--P in FIG. 1;

FIGS. 3a-3c show operational states;

FIG. 4 is a plan view of another embodiment of the driver;

FIG. 5 is a sectioned view on line Q--Q in FIG. 4;

FIG. 6 is a plan view of another embodiment of the drive;

FIG. 7 is a sectioned view on line R--R in FIG. 6;

FIG. 8 is a perspective view of an appearance of another embodiment ofthe driver;

FIG. 9 is a perspective view of an appearance of a mouth washerincorporating the pump driving mechanism of the present invention;

FIG. 10 is a view showing a state in which the mouth washer is used;

FIG. 11 is a sectioned elevation of the mouth washer;

FIGS. 12 and 13 are sectioned side views of the mouth washer;

FIG. 14 is a magnified perspective view of a timing pulley; and

FIG. 15 is a sectioned view showing a conventional water feeding device.

In FIG. 1, a driver 1 is illustrated, which includes a pair of flangepieces 2 fixing the driver 1 to the pump device, and a piston body 3 isdisposed between these fixing pieces 2. This piston body 3 is formed ofa piston base 8 formed as a rectangle with respective pairs ofelastic-leg bases 4 and 5 and supporting members 6 and 7 respectivelyprovided to oppose each other and a cylindrical piston rod 9 projectedon the side of the fixing piece 2 out of one of the elastic-leg bases 5.

In FIG. 2, the piston rod 9 is fixed by a stopper 13 on a shaft 10provided in the center of the rod and inserted into a hole 11 formed inthe elastic-leg base 5 and thereafter into a stopper-inserting hole 12formed in the elastic-leg base 5. An end edge of this shaft 10 is fixedto the piston body 3 and forms a pump 15 together with a cylinder 14(see FIG. 3). In FIG. 1, elastic leg pieces 16 and 17 are suspendedrespectively from the elastic-leg bases 4 and 5; their end edges areturned to be U-shaped again onto the side of the fixing pieces 2 andconnected to the fixing pieces 2. Fixing piece side 16a and piston bodyside 16b as well as fixing piece side 17a and piston body side 17b arerespectively formed to be of the same length. The elastic leg pieces 16and 17 comprise widened and thined elastic plates and are formed to behigher in the elasticity than the fixing pieces 2, elastic-leg bases 4and 5 and supporting members 6 and 7. An elastic arm 18 is provided asextended in parallel to the supporting members 6 and 7 toward theelastic-leg base 5 from the elastic-leg base 4 and is formed in aU-shape with elastic pieces 19 which are formed to be little flexiblewith respect to a compressive force in said extended direction but to beeasily flexible with respect to a force from lateral sides and areconnected with each other through a shaft bearing piece 20, while ashaft bearing 21 is formed at the center of the shaft bearing piece 20.Into this shaft bearing 21, an eccentric shaft 23 driven to be rotatedby a motor 22 (see FIG. 11) is inserted. Fitting holes 24 are formed inthe fixing pieces 2, and the driver 1 is fixed to a base 26 by screws 25fitted in the fitting holes 24. The driver 1 is formed with a syntheticresin molding of such as a polyacetal resin so as to render the abovereferred elastic fixing pieces 2, piston body 3, elastic legs 16 and 17and elastic arm 18 to be integral.

Further, the foregoing piston rod 9 is extended outward from theelastic-leg base 5 on the side of the extending direction of the elasticarm 18, whereby the moving directions of the piston body 3 in which theelastic arm 18 buckles coincide with the exhausting stroke of the pistonbody 3 in which the load of the pump is light so that the buckling ofthe elastic arm 18 will be prevented.

Operational states of the driver shall be explained next in thefollowings with reference to FIGS. 3(a), (b), and (c). FIG. 3(a) is aview of a state in which the eccentric shaft 23 inserted in the bearing21 has approached the supporting member 6, wherein the pair of elasticleg pieces 16 and 17 are not deformed but the elastic pieces 19 of theelastic arm 18 are deformed as flexed to the side of the supportingmember 6 with their elasticity. When the eccentric shaft 23 rotates fromthis state, as shown in FIG. 3(b), the elastic arm 18 will be deformedin response to the rotation of the eccentric shaft 23 and will come tothe intermediate position between the supporting members 6 and 7. On theother hand, the elastic leg pieces 16 and 17 will be deformed, thepiston body 3 will be made to approach the fixing piece 2 on the side ofthe piston rod 9 and the piston rod 9 will be inserted into the cylinder14. When the eccentric shaft 23 further rotates from this state, themovement of the piston body 3 will turn responsive to the rotation ofthe eccentric shaft 23, the elastic pieces 19 of the elastic arm 18 willbe deformed as flexed to the side of the supporting member 7 with theirelasticity where the eccentric shaft 23 comes closer to the supportingmember 7 but the pair of elastic leg pieces 16 and 17 are not deformed,thereafter the elastic pieces 19 of the elastic arm 18 will be deformedto separate from the fixing piece 2 on the side of the piston rod 9 andthe piston rod 9 will retreat from the cylinder 14 as shown in FIG.3(c). The eccentric shaft 23 rotates again to the state of FIG. 3(a)from this state of FIG. 3(c) and, with this rotation, the piston body 3makes one reciprocating motion to complete the operation of one cycle.That is, the flexing directions of the elastic leg pieces 16 and 17 andelastic arm 18 are different so that the elastic leg pieces 16 and 17will deform as bent in the reciprocating directions of the piston body 3and the elastic pieces 19 of the elastic arm 18 will transmitreciprocating directional components in the rotational movements to thepiston body 3 whereas, components in the directions perpendicular to thereciprocating directions, are in edgewise directions of the elastic legpieces 16 and 17 of thin plates and the elastic leg pieces 16 and 17 arenot deformed but the elastic pieces 19 are deformed as flexed to convertthe rotary motions of the eccentric shaft 23 only into the parallelreciprocating motions of the piston body 3 so as to have the piston rod9 reciprocally moved.

In the arrangement wherein, as has been referred to, the fixing pieces 2and piston body 3 are connected by means of the elastic leg pieces 16and 17 respectively formed integral with the fixing pieces 2 and pistonbody 3, the gears can be omitted in contrast to the conventional devicereferred to in the preamble so that the sliding places between therespective elements can be reduced and the drive can be made with alower noise. Further, the U-shaped elastic leg pieces 16 and 17 canrender the substantial length of the elastic leg pieces 16 and 17 to belarger within a limited space, whereby the driver 1 can be minimized insize, and any deformation load of the elastic leg pieces 16 and 17 perse is lowered so as to allow the piston body 3 to be reciprocally drivenwith a lower load. Further, the elastic leg pieces 16 and 17 connect thefixing pieces 2 and piston body 3 and are folded back at their centersto be a pair of U-shaped elastic leg pieces so as to have equal-lengthsides 16a and 17a and movable piece sides 16b and 17b. As a result,these fixing piece sides 16a and 17a and movable piece sides 16b and 17bof the respective elastic leg pieces 16 and 17 will flex by the sameamount upon the reciprocal movements of the piston body 3 since theirresistive moment are equal and the total height at the fixing piece side16a of the elastic leg will be made lower by this flexure, but itscontraction will be equal to the contraction of the total height at themovable piece side 16b of the elastic leg. Therefore, the folded-backparts will perform rocking movements. In the elastic leg 17, too, thecontractions of the fixing piece side 17a and movable piece side 17bwill be equal so that the folded-back parts will perform rockingmovements and the rolling of the piston body 3 will be cancelled withthe both folded-back pieces. Thus, the piston body 3 is caused to moveparallelly and the movements of the piston rod 9 can be stabilized. Theelastic leg pieces 16 and 17 are formed as beams of a uniform strengthso as to render the stresses to be substantially equal over their totalheights and total lengths, so that the maximum stress within the elasticleg pieces 16 and 17 can be made smaller. By varying the cross-sectionalarea over the total height or total length within the elastic leg pieces16 and 17 or by varying the thickness and width of each leg piece, thestress within the elastic leg pieces 16 and 17 can be made smaller.Further, the piston body 3 to which the elastically flexible elastic arm18 is fitted and in which the shaft bearing 21 is provided at the freeend of the elastic arm 18, except the pivoting part between the elasticarm 18 and the eccentric shaft 23, is to utilize the elasticdeformations of the elastic arm 18 and elastic leg pieces 16 and 17, sothat any other motion component than the reciprocating motion can beabsorbed by the elasticity of both of them or, specifically, by theelastic arm 18 and a very smooth reciprocating motion can be obtained.As the eccentric shaft 23 and bearing part 21 are round-hole-connectedwith each other, further, the clearance at the pivoting part can be keptalways constant, whereby an effect that any vibrational noise is muchlower can be obtained.

FIGS. 4 and 5 show another embodiment, which is different from the abovedescribed embodiment only in the following members. That is, aconnecting piece 27 connects the folded-back parts of the respectiveelastic leg pieces 16 and 17 and interferes with the respective elasticleg pieces 16 and 17 in case the thicknesses or widths of the elasticleg pieces 16 and 17 are different and the elasticity coefficient of theelastic leg pieces 16 and 17 become nonuniform, so that any rollingmovement of the piston body 3 due to independent and nonuniform flexuresof the elastic leg pieces 16 and 17 will be prevented from occurring andthe motion of the piston rod 9 will be stabilized. Coupling pieces 28are arranged respectively on both right and left sides of the supportingmembers 6 and 7 between the both fixing pieces 2 and, further, forkedelastic projecting pieces 29 are molded as integrally connected in themiddle parts of these coupling pieces 28. These elastic projectingpieces 29 and coupling pieces 28 are injection-molded together with thedriver 1 in the form shown by the double-dotted chain lines in thedrawing and then the coupling pieces 28 are turned as shown by the solidlines so that the tips of the respective elastic projecting pieces 29will be in elastic contact with both side surfaces of the supportingmembers 6 and 7. The elastic arm 18 having the shaft bearing 21 at theone end and flexible only in the right and left directions so as toabsorb the other motion components than those in the axial directions ofthe piston 9 is formed of a plurality of parallelly arranged filmyelastic pieces 19 which are thined close to the injection-molding limitand, by thus making them thin, the bending resistance to the flexure inthe right and left directions is made as small as possible. The pistonbody 3 of which the elastic-leg bases 4 and 5 at the front and rear endsare connected to the fixing pieces 2 through the elastic leg pieces 16and 17 U-shaped in the vertical plane reciprocates to move the piston 9within the cylinder 14 while being subjected to a resistance to therolling by the elastic projecting pieces 29 elastically contacting withthe supporting members 6 and 7 on the both side surfaces. As the elasticarm 18 is formed of the elastic pieces 19, even if the elastic pieces 19are made plural so as to be responsive to various loads, the bendingresistance in the right and left directions will be reduced so as torender the arm to be more easily flexible and, as a result, even a highspeed rotation can be sufficiently followed while unnecessary motioncomponents are absorbed, whereby the rolling applied to the piston rod 9is reduced and the life of the sealing between the piston rod 9 and thecylinder 14 is prolonged.

FIGS. 6 and 7 show another embodiment, which is different from the abovereferred embodiment only in the following members.

That is, a pair of coupling pieces 28 provided to bridge between theside ends of the both fixing pieces 2 are integrally molded so as to belittle elastic, and such rotors 31 as a miniature bearing rotationallycontacted with the side surfaces of the supporting members 6 and 7 aremounted to the respective tips of forked projecting pieces 30 extendedsubstantially out of the central parts of these coupling pieces 28.These rotors 31 act as a guide for the reciprocating motions of themovable piece 3 so as to prevent the rolling of the piston body 3 andpiston rod 9 without increasing the load, whereby a more accuratereciprocating motions are secured and the life of the sealing betweenthe piston rod 9 and the cylinder 14 can be remarkably prolonged.

In FIG. 8, still another embodiment is shown, in which a pair ofelastically flexible coupling pieces 28 U-shaped in a horizontal planeare provided respectively between the side ends of the piston body 3 andthe side ends of the fixing piece 2 in addition to the elasticallyflexible elastic leg pieces 16 and 17 U-shaped in the vertical planebetween the front end of the piston body 3 and the fixing piece 2, sothat the rolling of the piston body 3 will be prevented by the couplingpieces 28. In this case, the outside surfaces of bent parts projectingsidewise of the coupling pieces 28 are preferably guided by a base 26.

With reference to FIGS. 9 to 13, an embodiment of a mouth washer inwhich a pump using the driver of FIG. 1 is incorporated shall beexplained. A case body 32 containing driving parts and others isrecessed in the left shoulder part so that a tank 33 for storing watercan be removably mounted on this part. The tank 33 is formed in arectangular box shape opened on the upper surface and is contained inthe case body 32 by fitting a valve tube 34 projecting out of the lowersurface into a water feeding port 35 so that, by pushing up a valve 37with a pin 36 projecting out of the water feeding port 35, the waterwithin the tank 33 will be led into a suction port 38 of a reciprocatingpiston type pump 15 set below the tank 33 through the water feeding port35. A lid 39 is to removably cover the upper surface opening of the tank33, and a tubular shaft 41 is fitted to the lid 39 by fitting the upperend of the tubular shaft 41 onto a projecting tube 40 projectedsubstantially in the center of the lower surface of the lid 39. Thetubular shaft 41 is formed to be tapered with the outer diameter smallertoward the upper end and a radially expanding receiving dish 42 isformed on the outer periphery at the lower end, so that a nozzle 43 andtooth brushes 44 can be mounted as erected on the receiving dish 42.Here, the inner surface of the side wall of the tank 33 is also expandedupward so that, when the lid 39 is fitted to the tank 33 to house thereceiving dish 42 in the lower part of the tank 33 as shown in FIG. 11,a clearance between the tubular shaft 41 and the tank 33 will be widerin the upper end part a than in the lower end part b, the nozzle 43 andtooth brushes 44 will not contact the tubular shaft 41 and tank 32,particularly, even if the tooth brushes 44 rotate, brush bristles 44awill not contact the tubular shaft 41 and, when they are not used, theycan be sanitarily contained in the tank 33. A recess 45 is providedannularly on the upper surface of the lid 39 so that the lid 39 will beremoved and fitted by inserting fingers into this recess 45. A pump 15and motor 22 are fitted respectively to a base 26 fitted to an openingon the lower surface of a tube body 32. The base 26 watertightlyconnects the base plate 26 and case body 32 by fitting a projection 46projecting upward from the peripheral edge into a groove 47 in the lowerend surface of the peripheral edge of the case body 32 in a so-calledfaucet type. A circular recess 49 opened on the front surface of thecase body 32 is provided in a projecting part 48 in the upper part ofthe case body 32. A tube body 50 closed on the front surface and openedon the rear surface inside the case body 31 is projected forwardsubstantially from the center of the bottom wall of the recess 49located deeply inside the case body 32. A forward and rearward longannular housing chamber 52 of a diameter substantially equal to the coildiameter of a curled hose 51 is formed between the inner peripheral wallof the recess 49 and the outer peripheral wall of the tube body 50. Thecurled hose 51 pulled out of the lower part of the inner bottom wall ofthe housing chamber 52 is to be wound on the outer periphery of the tubebody 50 and housed in the housing chamber 52. Thus the curled hose 51wound to be in a coil shape is housed in the housing chamber 52 providedto be recessed within the case body 32 with the axis of the coildirected in the front and rear directions. Thus, the direction in whichthe curled hose 51 extends and the direction in which the user actuallyremoves a gripping part A from a holding part 53 coincide with eachother. Also, the elongation of the curled hose 51 thus becomes maximum,and the operatability improves, i.e., it will be easy to use even if thecase body 32 is arranged in, for example, the inner part of a toilettable. Furthermore, as the curled hose 51 can be housed in the housingchamber 52 recessed within the case body 32, the volume of the entiredevice including the hose 51 or particularly the width in the front andrear directions can be made smaller. A current source transformer 54 ishoused within the tube body 50 opened on the rear surface into the casebody 32. The motor 22 is housed below the recess 49 and the pump 15 ishoused in the case body below the tank 33 so that, by arranging thesethree bulky parts 54, 22 and 15 in an L-shape in a vertical plane, thefront and rear width and right and left width of the case body 32 can bemade as small as possible within a range of allowance. A lid 55 isfitted to the rear surface of the case body 50 by means of screws 56 asshown in FIG. 12 waterproof packing (not illustrated) such as an O-ringis fitted over the entire periphery of butting part between the lid 55and the tube body 50 to watertightly close the tube body 50, and allsuch other electric parts as the current source transformer 54 and thelike than the motor 22 are fitted en bloc on a printed base board (notillustrated) and are housed in this case body 50. Load wires (notillustrated) for electrically connecting these electric parts and thepump 15 or gripping part A are pulled out of the case body 50 throughwaterproof bushes (not illustrated) provided at one place of the jointof the tube body 50 and lid 55 so that the electric parts within thetube body 50 will be protected from an entry of water and anyshort-circuiting due to water entering the tube body 50 can be preventedfrom occurring even if the case body 32 is all wet while the electriccurrent is being passed. The motor 22, set on a supporting beam 57projecting out of the base 26 of the case body 32, rotates a timingpulley 58 on the driving side arranged adjacent the base 26 of the casebody 32. A timing belt 59 engaging with this timing pulley 58 rotates atiming pulley 61 on the driven side rotatably supported by a shaft 60 onthe base 26 below the tank 33 and placed on the same plane as the timingpulley 58. The eccentric shaft 23 projecting above the shaft 60supported at shaft part 62 by the base 26 drives the piston body 3, andthe pump 15 is driven by a conversion of the motion component renderingthe rotary motion to be the linear reciprocating motion by the pistonbody 3. A partition plate 63 is erected from the base 26 between themotor 22 and pump 15, and an adjusting screw 65 is screwed from the sideof the pump 15 into an inserted nut 64. The tip of the adjusting screw65 contacts the motor 22 to press it rightward in FIG. 11, whereby theposition of the timing pulley 58 on the driving side for the timingpulley 61 on the driven side is finely adjusted to keep the tension ofthe timing belt 59 proper, to prevent any tooth skipping, resonance,pulley disengagement and the like from being caused due to any loosenessof the timing belt, and to prevent the motor load from being increaseddue to any over tightness of the belt. Further, this adjusting screw 65prevents the motor 22 from being moved to the loose side of the timingbelt 59 by a dropping shock. The both timing pulleys 58 and 61 engagingwith the timing belt 59 for transmitting the driving power between themotor 22 housed on the righthand side of the case body 32 and the pump15 housed on the lefthand side are provided on the upper and lower endsurfaces respectively with upper and lower flanges 66 and 67 to preventthe timing belt 59 from being disengaged. The upper and lower flanges 66and 67 projecting in the peripheral direction are divided respectivelyin a plurality of sections by incisions 68 so that, as shown in FIG. 14,the lower flange 67 will be formed within the angle of the incision 68of the upper flange 66 and the upper flange 66 will be formed within theangle of the incision 68 of the lower flange 67.

The pump 15 having received the power of the motor 22 through the timingbelt 59 feeds the water within the tank 33 to a nozzle 43 fitted to thetip of the gripping part A through the curled hose 51 and anintermittent jet water stream jetted out of the nozzle body 43 washesthe mouth. The tooth brush 44 is also fitted to the gripping part A sothat, in this case, the tooth brush 44 will be driven by a motor (notillustrated) within the gripping part A so as to function as a so-calledelectric tooth brush. This motor within the gripping part A iselectrically connected to the current source transformer 54 throughcurrent source wires formed integrally with the curled hose 5. 69 is ahydraulic pressure adjusting knob for adjusting the pressure of waterjetted out of the nozzle.

With the device wherein thus the motor and pump are separated from eachother and the timing belt is used to transmit the power between them canbe made to be of a thin type in which any restrictions to thearrangement of the driving parts are made less and the substantial depthcan be determined only with the width of the motor while the height canbe controlled. As the pump is arranged just below the tank, further, thepump and tank can be connected directly with each other so that theparts for the internal water path for which waterproofness must beconsidered can be reduced. Further, as the timing belt is used totransmit the power, the operation can be made smooth, a high hydraulicpressure can be obtained without involving any slipping and a highperformance can be maintained.

We claim:
 1. A driving mechanism for a fluid pump of the type comprisinga fluid-conducting cylinder, said driving mechanism comprising:a pair ofelastically flexible generally U-shaped leg means, each including firstand second legs which flex toward and away from each other about a bendat which said first and second legs are joined, said first leg of eachleg means being fixed at a free end thereof, with the free ends of saidsecond legs opposing each other, a piston body coupled to said free endsof said second legs so as to be reciprocable in a fore-aft directionbetween said fixed free ends of said first legs, said piston bodycomprising a rigid generally rectangular shaped frame having opposingends spaced in said fore-aft direction, a piston rod connected to saidpiston body and arranged to be reciprocable in said cylinder in adirection parallel to said fore-aft direction for pumping fluid throughsaid cylinder, and elastically flexible arm means connected to saidframe and disposed therewithin, said arm means including meansconnectible to an eccentric motor-driven shaft, said arm means beingelastically flexible in directions transversely of said fore-aftreciprocable direction and being arranged to transmit motion to saidframe in said fore-aft direction.
 2. Apparatus according to claim 1,wherein said first and second legs are of substantially equal length. 3.Apparatus according to claim 1, wherein said frame includes sideportions spaced apart in said transverse direction, and guide meansconnected to said fixed legs and arranged to exert guiding forces onsaid side portions to resist movement of said frame in said transversedirection.
 4. Apparatus according to claim 1, wherein said piston rod iscoplanar with said frame.
 5. Apparatus according to claim 4, whereinsaid first leg of one of said leg means includes a recess through whichsaid piston rod extends.
 6. Apparatus according to claim 1 includingsaid drive motor having an outlet shaft extending parallel to saideccentric motor-driven drive shaft, a first timing pulley coupled tosaid outlet shaft, a second timing pulley coupled to said eccentricshaft, and a timing belt drivingly interconnecting said first and secondpulleys.
 7. Apparatus according to claim 6, wherein said leg meansproject beyond the plane of said frame in one direction, said timingbelt being spaced from the plane of said frame in the oppositedirection.
 8. Apparatus according to claim 1, wherein said arm meanscomprises a pair of parallel arms, each arm comprising a plurality ofparallel spaced apart arm pieces to maximize the flexibility of said armmeans in said transverse direction, and a transverse memberinterconnecting the free ends of each arm.